Some system devices such as memory may operate in various power consumption modes such as active, standby, and off. These power consumption modes of these devices coincide with and are globally controlled by the power consumption mode of the overall system. If the entire system is off, then all of the components of the system such as disk drives, processors, are powered off. If the entire system is in a standby mode, then most of the components in the system are in a reduced consumption mode. If the entire system is in an active mode, then all of the components in the system are in a fully powered up state.
In some systems, all controllers going to devices, such as the memory and Universal Serial Bus (USB) ports, are enabled and powered even if nothing is attached to these controllers. As such, the controllers consume power through 1) leakage, 2) their internal switching circuitry (CV2F), and 3) the physical layer drivers. The controllers typically remain powered because they support some sort of plug in event and the controllers need to understand when a device may be plugged into the controller. As such, these controllers are seldomly powered off in the system and tend to lend themselves to a steady power addition to the overall power consumption of the device.
While the invention is subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. The embodiments of the invention should be understood to not be limited to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.